The present invention relates generally to in-situ inspection of rotating machinery components and, more particularly to in-situ ultrasonic inspection of turbine and compressor components, for example, blades, buckets or airfoils in turbines and compressors.
At least some known gas turbine engines include a compressor for compressing air, which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. The hot combustion gases are channeled downstream to a turbine, which extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
Known compressors include a rotor assembly that includes at least one row of circumferentially spaced rotor blades. Each rotor blade includes an airfoil that includes a pressure side and a suction side connected together at leading and trailing edges. Each airfoil extends radially outward from a rotor blade platform. Each rotor blade also includes an attachment portion, such as, a dovetail that extends radially inward from the platform, and is used to mount the rotor blade within the rotor assembly to a rotor disk or spool.
During operation, the rotor blades and dovetails are subjected to loading forces that may cause in-service cracking, micro-fractures or other damage that is visually imperceptible. Known inspection techniques are limited in their ability to assess the integrity of the blades while the blades are in-place. More specifically, a visual inspection only permits a limited examination of the blades for cracks in the airfoil. To thoroughly examine the blade and dovetail regions, where cracking or other damage may originate, at least a portion of the engine casing may need to be removed to facilitate removal of each blade, and subsequent inspection of the blades and dovetails with visual, magnetic particle, liquid penetrant, or other techniques. However, because of labor and cost constraints such techniques may be impracticable in some instances. To examine the blades without disassembly, a technician must manually reach into the machine. This can be a potentially hazardous action as any movement in the rotor blades or inlet guide vanes would likely result in the loss of a limb. Accordingly, a new method and apparatus for the in-situ inspection of rotating machinery components is needed.